A radar target simulator is used in the laboratory or in an anechoic chamber in conjunction with a radar for testing the accuracy, susceptibility to glint, etc. A complex radar target such as an aircraft or ship at any instant of time appears as a collection of point reflectors located at the reflection centers of the various geometric shapes comprising the target. As the target rotates relative to the radar line-of-sight due to angular motion of the target or linear motion of the radar or target, the path lengths to the reflection centers and therefore, the phase shifts in the returns from the reflection centers vary. The multiple returns coherently add or subtract to produce amplitude peaks and fades in the total received signal and distortions in the phase front of the received signal at the radar antenna. The former effect is termed amplitude scintillation and the latter effect is termed angle scintillation or angle glint and also produces the scintillation in Doppler frequency. The present invention is designed to simulate Doppler frequency scintillation in a radar target.
A simulator which generated continuous time random noise representing the fluctuating power return or radar cross section of a Swerling case 1 or case 3 target type was previously developed by the assignee of this application. The previous simulator was incapable of generating target Doppler frequency scintillation. Whereas target amplitude scintillation is very important in the detection process, target Doppler frequency scintillation is of great importance in the Doppler tracking process since it produces target spectral spreading and dictates the bandwidth and other characteristics of the Doppler tracking loops in a coherent radar.